Supplementary file 1_Compound extremes: variability, drivers, and coping mechanisms over semi-arid catchments in Central India.pdf

Rainfall and temperature variability serve as crucial indicators of hydroclimatic hazards, including floods, droughts, heatwaves, and cold spells. While such events may arise from a single variable reaching extreme levels, they often result from the interplay of multiple climatic factors. This study examines the spatio-temporal variability of compound extreme events (CEEs) over the semi-arid Ken and Betwa River catchments in Central India. Although these regions primarily receive rainfall during the Indian Summer Monsoon (ISM) season, they have experienced a post-2000 drying trend along with rising temperatures. A significant negative correlation between rainfall and temperature indicates rainfall suppression under hotter conditions due to enhanced atmospheric stability and reduced moisture availability. The analysis further shows that extreme wet and dry events have declined in the Betwa basin, while the Ken basin exhibits an increase in extreme dry events and a decrease in wet extremes. Cold extremes (T10) have also shown a decreasing trend across both regions. Investigation of different combinations of rainfall and temperature extremes reveals that moderate and extreme warm-dry CEEs have intensified over the past four decades, emerging as the most dominant compound events. The persistence of these events is largely driven by wind patterns and convective inhibition energy (CIN) in the case of moderate events, and by moisture transport and divergence for extreme ones. The intensification of such CEEs poses substantial risks to regional agriculture, eco-hydrological systems, and socioeconomic stability. Composite Resilience Index (CRI) was developed at the district level, integrating indicators like the Human Development Index, Multidimensional Poverty Index, and literacy rates. Results reveal that Ashoknagar, Shivpuri, Lalitpur, and Chhatarpur are the relatively low-resilience districts, while Bhopal, Sagar, Jhansi, and Hamirpur exhibit higher resilience. Overall, the findings underscore the urgent need for climate-informed policies and adaptive strategies to ensure water sustainability and socio-economic stability in the Ken–Betwa river catchments under a warming climate.